The new Harry Potter book, Harry Potter and the Cursed Child (parts I and II) does not have an official release date, but it is said that the book will be released sometime in the summer, after the world premiere of the play. The new book is a written version of the play that will be performed for the first time on July 30th.

Harry Potter and the Cursed Child starts right after we see Harry sending his kids off to Hogwarts, which is in the epilogue for Harry Potter and the Deathly Hallows.